OWA 2010 cannot open 2007 mailbox

As you know, as long as you have the proper permissions you can access another users’ mailbox using OWA.

However, if you are in the middle of a migration from Exchange 2007 to 2010 and you have deployed Update Rollup 1 for Exchange 2007 Service Pack 3 you will find that a user in 2010 cannot open a 2007 mailbox even though he/she has Full Access permissions to it...

When I login to OWA using my Nuno account (in 2010) and try to open the Mota mailbox (in 2007) I get the following error:

This is because Rollup 1 introduces the following “fix”:

976100 - Shared calendar items are shown incorrectly in the server time zone instead of the time zone of an Exchange Server 2007 user who is accessing the shared calendar

“Consider the following scenario:

• User A and User B are Exchange Server 2007 users;

• User B shares a calendar with User A;

• User B grants User A read access permission to the calendar;

• User A accesses the shared calendar of User B by using Outlook Web Access (OWA).

In this scenario, the shared calendar items are shown in the time zone of the server instead of the time zone of User A. However, if User A has full access permission to the shared calendar of User B, the calendar items are shown in the time zone of User A.

This problem occurs because the time zone information is stored in a configuration message that is in the root of the mailbox. A user who does not have full access permission to a shared calendar, cannot access the time zone information. Therefore, the server time zone is used.”

After this Rollup is installed, you can control the time zone at the Organization level by running the Set-OrganizationalSetting cmdlet together with the SharedCalendarTimeZone parameter. Principal, Delegate and UserConfigured are the three values for the SharedCalendarTimeZone parameter which, by default, is set to UserConfigured.

If the parameter value is set to Principal, the time zone is shown in the principal’s time zone. If set to Delegate, the time zone is shown in the Delegate’s time zone. If set to UserConfigured, the user can follow these steps to change the time zone to the delegate’s time zone or to the principal’s time zone:

• Log on to OWA, and navigate to the Options page;

• Check the default value for the shared calendar time zone;

• Select the value for the "When viewing a shared calendar, show items in:" drop-down list to Delegate Time Zone or to Principal Time Zone.

Note: when you configure the SharedCalendarTimeZone parameter to either Principal or to Delegate by using the Set-OrganizationalSetting cmdlet, the option to configure the time zone in OWA is disabled.

Resolution

To fix this issue, all you have to do is run the following command from a 2007 server to set the SharedCalendarTimeZone to Principal (which is the only option that fixes this issue):

Set-OrganizationalSetting –SharedCalendarTimeZone Principal

Note: Please test this change before deploying it to your live environment as it might confuse users if they are spread across different time zones!

Hope this helps!